This invention relates generally to apparatus for cooling electronic assemblies and, more particularly, to cooling apparatus configured to direct air to flow across the electronic assemblies.
Apparatus of this particular kind are used in a wide variety of electronic equipment, especially equipment incorporating microprocessors, which can generate significant amounts of heat. Typically, such equipment mounts the microprocessor and other heat-generating components on one or more printed circuit (PC) boards, with one or more heat sinks also mounted on the board. A fan or blower directs a tangential flow of air across the PC board and heat sinks, to cool the components by convection. Properly cooling each microprocessor typically requires a volumetric flow of about 10 liters per second, at a velocity of about 2 meters per second.
Heat dissipation is a more difficult problem to address when the electronic equipment incorporates numerous microprocessors or other components and modules generating large amounts of heat. Some high-end servers, for example, can house as many as 64 microprocessors, with associated memory devices and ASICs, dissipating up to 12 kilowatts.
In such cases, cooling apparatus of the kind described briefly above are necessarily very large and complex. In addition, the tangential, unidirectional nature of the air flow causes the multiple components to be cooled in series. Consequently, the downstream components are cooled by preheated air and thus are cooled by lesser amounts than are upstream components. This drawback is alleviated somewhat by using a high air flow rate and by using heat sinks having large surface area. Heat sinks measuring 125 mm by 125 mm by 40 mm are commonly used. The large bulk volume flow also can require the use of several blowers and large exhaust ducting. The resulting size and complexity have detracted significantly from such electronic equipment's commercial viability.
It should, therefore, be appreciated that there is a need for an improved cooling system for high-performance electronic assemblies of the kind incorporating multiple microprocessors or other heat-generating components and modules, which is substantially smaller in size and less complex, yet which is reliable and effective in dissipating excess heat. The present invention fulfills this need and provides further related advantages.